1. Field of the Invention
The present invention relates to an engine that is equipped with an exhaust manifold being integrally formed with a cylinder head, and more particularly to an engine in which exhaust efficiency thereof is improved.
2. Description of Related Art
Generally, an exhaust manifold is developed as a separate component and is assembled to an engine, but it can affect the overall performance and durability of the engine.
The exhaust manifold not only needs a gap from surrounding components so that it does not heat them excessively, but it also requires space to house it in the engine compartment.
Also, a catalytic converter that is disposed downstream of the exhaust manifold needs to be installed close to the engine so as to be activated by the heat. Accordingly, the exhaust manifold and the engine need to be compact.
As the number of cylinders increases, as an example, there is a problem in that the low speed torque that is an important characteristic of the engine is decreased by exhaust pulsation resistance in an in-line four cylinder engine.
FIG. 6 is a schematic diagram and a table showing a general four cylinder engine and an exhaust stroke thereof.
As shown in the left schematic diagram of FIG. 6, the engine includes a first cylinder #1, a second cylinder #2, a third cylinder #3, and a fourth cylinder #4. Also, an intake side and an exhaust side of respective cylinders are connected to a turbocharger 600 and 605.
As shown in the right table of FIG. 6, an expansion stroke is sequentially operated such as the first cylinder #1>the third cylinder #3>the fourth cylinder #4>the second cylinder #2. Accordingly, as shown in the table, one interval (EVO-EVC) in which an exhaust valve is open in the first cylinder #1 and another interval EVO-EVC in which an exhaust valve is open in the second cylinder #2 are overlapped.
Accordingly, the exhaust valve is open in the first cylinder #1 until the exhaust valve is closed in the second cylinder #2, and at this moment there is a problem in which remaining gas of the second cylinder #1 is not efficiently evacuated because of a high exhaust pressure of exhaust gas that is exhausted from the first cylinder #1.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.